You’ve finally chosen to pay a visit to the doctor for the pain in your gut or that weird swelling in your neck. After all, you’ll probably just leave with a prescription and be on your way, right? If the doctor hands you a referral to have an ultrasound instead, don’t panic.

The imaging procedure is often associated with OB-GYN issues like pregnancy, but it’s not just for moms-to-be. Primary care or hospital physicians might refer you to a sonographer for an ultrasound to scan blood flowing to your heart, veins or vessels or to take a closer look at your abdominal area.

“Ultrasound is used from the top of the head to the bottom of the feet,” says Dr. Laurence Needleman, director of ultrasound at Thomas Jefferson University Hospital in Philadelphia, adding that scans can also be done on the thyroid gland, liver, spleen and kidneys.

The imaging, also called scanning or sonography, can help physicians pinpoint the reason for pain, swelling and infections, check internal organ functions or guide biopsies to detect cancer by using a small transducer — or probe — and ultrasound gel applied to the skin. High-frequency sound waves transmit an image to a machine in real time. In biopsies, the ultrasound can be used to visualize the area of concern, according to the Radiological Society of North America.

Although ultrasounds vary by type, consider these points to prepare for your first ultrasound appointment:

Check credentials. “The two major ways you can tell you’re in a better quality laboratory is if the technologist is registered and if the laboratory is accredited,” Needleman explains. “That improves your chances of being scanned by somebody who is qualified.”

Look for the RDMS credential behind a sonographer’s name for abdomen, breast, fetal heart, obstetrics and gynecology, or pediatric scans. For scans mostly related to the heart — or echocardiography — the sonographer should have the RDCS credential. Other credentials, like RVT, are for vascular — or vein — scans; RMSKS is the credential you should see when getting muscle or bone scans, according to the American Registry for Diagnostic Medical Sonography.

You might need to fast. In some instances, you might be told not to eat or drink for several hours before your appointment, says Dr. Deborah Levine, director of OBGYN ultrasound at Beth Israel Deaconess Medical Center and Harvard Medical School in Boston.

“If you eat, your gallbladder will contract, which is normal, but we want to look at the gallbladder when it’s not contracted,” Levin says, adding that the same might be the case for prostate or vaginal ultrasounds.

For some ultrasounds, you may be told to drink more water than usual and avoid going to the restroom so the bladder is full when the scan begins. “Anything different will be told to the patient ahead of time,” Levine says.

What to wear. The ARDMS suggests wearing comfortable clothing for the exam. However, be prepared to remove clothing over the area of the scan, Levine says.

“A woman having a pelvic ultrasound who is post-menopausal might be uncomfortable with having a vaginal ultrasound,” Levine says, adding that women can always refuse a procedure. “Frequently, we do end up spending extra time reassuring patients on studies like that.”

There’s no radiation. “Ultrasound is an imaging test that works very well for many different organs in the body that allows us to see and examine those organs in a very effective way. Different than other imaging studies we have, such as X-rays or CT scans, ultrasound has a great advantage in that it doesn’t involve any harmful radiation,” says Dr. Salomao Faintuch, a staff radiologist in vascular and interventional radiology at Beth Israel Deaconess Medical Center and Harvard Medical School in Boston. “All it uses is sound waves that come into and out of the body.”

Faintuch explains that the gel helps transmit sound waves from the probe touching the patient’s skin to the machine. “Ultrasound scanning therefore does not involve any injection or pain. It does not really involve any known risks to the person being scanned,” he says.

Ask questions. The sonographer completes the scan, but the radiologist analyzes the images and sends a full report to the primary care physician or other health care provider who referred you to have the test. Results are usually given within three days or less.

It’s important to remember that not every facility will provide you with results right away. In hospital settings, this may happen more quickly than an outpatient center, Needleman says. “You can ask to know what [the scan] is showing — whether it’s good news or bad news,” he explains. “It’s not available in all places.”

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What You Should Know About Your First Ultrasound originally appeared on usnews.com